We propose to isolate mutants of the simple nematode Caenorhabditis elegans defective in chemotaxis, in pharyngeal pumping, and in head movement. We propose to analyze these mutants both by behavior and by serial section electron microscopy and three-dimensional reconstruction. These types of mutants have been chosen because of the relative ease of determining whether they harbor synaptic alterations; our interest lies primarily in mutants which affect the specificity of synapse formation. We also propose to study the roles of neurotransmitters in the C. elegans nervous system by injection of pharmacological agents through the cuticle with micropipettes, to overcome the permeability barrier of the C. elegans cuticle. And we hope to carry out ablations of single cells in the C. elegans nervous systems, using a laser microbeam, to determine the roles played by those cells in behavior. Finally, we hope to study cell lineages during C. elegans development.